CVE-2026-129113: Integer Underflow

Description

JSON::XS versions from 4.0_00 before 4.05 for Perl corrupt the incremental buffer length by chopping past its end in incr_skip after a top-level number. The incremental parser scans any run of digits, signs, dots and exponent markers as one number, but the decoder stops at the end of a valid number, so the parser keeps an offset into bytes it has not decoded. It then empties the buffer without clearing those bytes, and a later incr_parse call without new input reads them again and moves the offset past the end of the buffer. incr_skip, the documented recovery after an error, removes that many bytes and the buffer length wraps. A peer sending input such as "1-2" to an incr_parse consumer can make the next read of incr_text exit the process through perl's uncatchable out-of-memory path.

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Weakness Type (CWE)

CWE-191 CWE-191

References

Other References

https://metacpan.org/release/MLEHMANN/JSON-XS-4.05/changes

Frequently Asked Questions

What is CVE-2026-129113? +

JSON::XS versions from 4.0_00 before 4.05 for Perl corrupt the incremental buffer length by chopping past its end in incr_skip after a top-level number. The incremental parser scans any run of digits, signs, dots and exponent markers as one number, but the decoder stops at the end of a valid number, so the parser keeps an offset into bytes it has not decoded. It then empties the buffer without clearing those bytes, and a later incr_parse call without new input reads them again and moves the offset past the end of the buffer. incr_skip, the documented recovery after an error, removes that many bytes and the buffer length wraps. A peer sending input such as "1-2" to an incr_parse consumer can make the next read of incr_text exit the process through perl's uncatchable out-of-memory path.

How do I check if I'm vulnerable to CVE-2026-129113? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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